Flame angle gets my vote as they are for ever on the move and entertaining but they need alots of algae to grase on as they go around the tank they are constintly nibbling on it. Over time they would eradicate a HA problem in smaller tanks. Marshal islands FA are a bit redder but as for them being reef safe they are all hit and miss a potters angle is about as reef safe as it gets. With any of these small angles if there is not enough algae they will pick on the corals they have to eat and they eat alot. If you can get a male and female you can keep them in the same tank other wise I would not. one pygmy angle that you can have more than one in the same tank is the (yellow fin, pacific pygmy angle or blue velvet angle) same fish different name.

Bill